This blog, as well as several other StackOverflow posts, say that usbfs has been deprecated since Ubuntu 9.10. If that is the case, what is /sys/bus/usb/drivers/usbfs doing there?

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    On another note, people sometimes forget to follow through on deprecation. My favorite example: bash supports a syntax for arithmetic expressions $[...] that is essentially equivalent to the standard $((...)). If you dig through the Git repository for bash (which dates back to 1996), you find no mention of the syntax in the man page, and a note in the NEWS file regarding bash 2.0 at the time saying that $[...] is no longer supported. Yet support remains in bash 5.0, released 14 months ago. – chepner Mar 19 '20 at 13:36

The deprecated usbfs refers to a pseudo-filesystem which was typically mounted under /proc/bus/usb and was completely removed from the kernel with the 3.5 release.

However the functionality provided by the old usbfs filesystem is still present, via sysfs and the “usbfs driver”.

So what was deprecated was the separate filesystem; the functionality survives in a different location, and isn’t deprecated.


Probably because it hasn't been removed. "Deprecated" means that you are discouraged from using the technology, and there is a plan to eventually remove it some time in the future. It does not mean the technology has already been taken away.

Some products will deprecate a feature in one release, and remove it in the following one. In some cases a lot of people continue to use the deprecated feature and so it stays on to give them time to transition to a different way of doing things.

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